Stereoscopic acuity testing device



Dec. 18, 1945. J, KOCH 2,391,248

STEREOSCOPIC A CUITY TESTING DEVICE Filed NOV. 7, 1942 FfgJ l4 I INVENTOR Gear edkoch M ZORNEYS Patented Dec. 18, 1945 2,391,248 i I szrmnoscorrdzmm'rr 'resrme nevren George J Z Koch, Rbchestery N. Y., assignor to Eastman Koflak:Gompanw-Rbehesfiw, N. Y5, a: corporation; N ewe J ersey Application November 7, 1942,.seria1 ,mtrsessz;

4=c1eims-.- (e1; sis-20 "I -he present.inventionz'relatesto. visual. testing. devices, and. more particularly to stereoscopic. aeuit-xtestingrdevicesn 'Ilhe. present" invention has, thereiore, v as its. principal. object, the; proyisiom of; a.. device. for. testingthestereoseopieacuity of an individuals 7 miurrther. object-.ot the inventionis thefpro. vision-oi astereoscopic'. acuity testing, deviceim which apain of. indiciasare; spaced. at. distance. the magnitude of which corresponds-toa.stereoseopie angle. eithe; same; order as. th limit. f;stereo- Fig.4, is; horizontal. sectionaljview througha steneeseopic acuity testing-device. constructed.- in: accordance with the present invention;

Fig. 2 is a'front view of the portion dithedevices-Which;carriesrtheeindiciasor marksrwhich are trrrh wiewed-by-the;obserrgcrg; i I a this :-a@ perspective, Viewr of. a.. comp1ete dee vicesil-lustrated inrF'ign 1,. showing the. arrange. ment, oi-thecvarious -parts;.and 7 p ;E1ig..4 isiaa. planview oi ar-grouppf .thedevices. oti thegeneral typeillustrated.ineEigsr 1. to i 3, [and mounted-imaisingle. holder, to provide onegroupp-- ingg on arrangen ent of;v the; various devicesi.

'llhe; presenuinvention relates; to. a. device for. testing the,- stereoscopie acuity.- oi a person. to. be examined. 'llofsecure. this; resulh two or :rnore distinguishable; indicia marks v on pictures, are arranged ihrspaced relation sogthatwhen viewed the. person both. indicia willtbe;v seen; each. eye thetwoteyeimagLes -veill .beangularW spaced. asgshownsinsEigl 1, so that-.-the.- physical. spacing or; depth.position 0 ;idzredndicia3 may. be. asserts: tainecL. In..or'der.thattsuchmarksmayf be read:- ilz'tstereoscopically,distinguishable onmmarlemam b intthe. form of.- a..1ine...and.the1-7other; marksa. planar figure, .on they may,-. be. in. the .iorm or. two,

lines. arranged-oneabovethe...other;.

'flie testris. carried showing theperrtoQbeetested a; seriesl ofr devices. of. the. type tem mfis e i' sewsh di i er be spacedl the/same. or difi'erent..distances,-. and. asking the person to judge the spacing or depth position of. thesindicia or. to distinguish. which,

devices havetheindicia. equalht spaced. @bS/ir. ously ehy; number; and arrangement. of. these.

devices; may, be. used! in; a: test, and; the. structure;

of: stereoscopie vision. By; means: at. such a. sew

ries. of: devices;,,thestereoscopic acuity? of. themes.- son being tested can; be; quickly easilm. and. ac.- curately: and definitely3 ascertained... The; extent of; such tests. may be: varied to. suit the: require:- ments: to: be':met..or.- the; person. being; tested.

'Eheindicia are=preferabl3y opaque-. andrmay; be printed. or; etched: on opposite. f aces; of; a. trans.-

parent. base: on spacer; sheet such: as; cellulose 1 acetate. or may be reproduced. phetographically. on; opposite side-of; astransparenmfilmrbase. In the; present. embodiment, one; of. thezindiciaz-masg bee i'mthe: form. of; a. reticieumark: th formed! on.

the face ll: of. the; transparent; spacer sheen. l3; IF-heathen indiciatmaxbe; for-example; aplanar figure: in the; form. or; am. aeroplaneaimage Ids-artrangedaon theeoppositezface [5;oithespaeensheet; I3, as-rshowmin Eieeh 'l'ihesspacingmfwthezindicia I 1' I111 is.th11s-: determined. thezthicknessmi th'e spacertsheet 13:. 'tawill news-bee anparent from-aminspectionv.ofi Ffi'g; 1 .that: buti'nindicia: tlh'aml: lhwillzbe visible toith'ea right eye. I6 andialse: tozthedeit' eye; II of? the person; being; tested... However; the: two. in'diciaz II: and; M'f'Will subtend'; angle;- lB at the: left eye: l1; assciearlyshownzirr Eigithn By} means of this ang1e;..the;spacing; or; depthtposie tiorr-Ioff the: twee i'ndicia; may: bee thereby ascentained. The angles t8; .knowmastheisteneoscopic: angle, is: controlled; 1m vargin thickness: of the. spacer sheet; I13: to: provide. at varying-depth or: positioncofz the: two: marks: M: and It. Since; the; anglez t8 is:alsorinfluencedbmxthe;vtewingdisatance, ,therimeroeulan spacing; of theeesges: lir; and. l'k and therefractive; indexzof the spacervv sheet. 13;. thesezfactore are. to be considered, inmaking; the device. I

It; has; been. found.- that. withv a viewing; dis:

tance. oi; 10. inches at. normal. mtenocular. space.v

separation ofthe marks" l1 and" MT Tire-term;

the stereoscopic angle [8 will-be approximately 0.075 unit of error for .001 inch of separation of the marks II and 14. The thickness of the spacer sheet varies between 0.001 inch and 0.02

inch. Such an arrangement of marks and spacer sheets has proven successful in a large number of tests.

In order to eliminate surface reflection cues, and to prevent scratching or fingerprinting of the indicia marks II and I4, twoadditional transparent non-polarizing sheets l9 and may be laminated to the surfaces l2 and I5 of the spacer" sheet 13. ,If desired, the indicia Hand I4 may be *formedon the inner faces of the sheets l9 and 20 rather than on the spacer sheet 13. In ither event, the indicia are actually spaced the thicknessof the sheet 13, as will be apparent from an'inspectionof Fig. 1. A transparent lacquer coating may be substituted for the protective sheetslB- and 20, if so desired. The laminated transparent sheets with the opaque indicia I l and diffusing screen 21. A series of these completed testing devices, as shown in'Figs. 1 to 3, may be mounted in a urgeperforated support or holder 25, such as cardboard, so that a number of these devices may be -readily available. Fig. 4 shows one of these arrangements. A number of these devices and 7 M are preferably backed by a translucent light the spacing of the indicia may be varied to any desired extent. For example, one cardboard holdermay have-mounted thereon a plurality of such devices in which the spacer sheets 13 are of 'equal thickness, but with some of the devices arrangedfwith the marks II on the front face and the: aeroplane 14 on the back face, while others may have the aeroplane on the front face andthe mark H on the rear face, and still others may-have both marks on the same face. This willprovide equal spacing but diiferent arrangements of the two "marks, and the person being tested is merely to determine in which device the mark II is in front of the aeroplane, and in which device the'mark I I'is behind the aeroplane, or in which device the two marks are in the same plane..-A second cardboard or :a series of cardboards may be provided'in which the various devices may have the marks H and I4 arranged as above, but in which the thicknesses of the various spacer sheets I3 may vary to give different spacings of the marks. The observer is then to determine not only which marks II an M are in front, but also on which devices the two marks aredifierently or equally spaced.

. The test is usually started with a cardboard in which a series of devices with relatively thick spacer sheets I3of equal thickness are provided. In this initial test only the position of the two marksis varied. On succeeding cardboard holders, however, the thickness of the sheets I3 may be gradually decreased to thus decrease the stereoscopic angle 18 between the marks. This decreasing sheet thickness may be combined with different arrangements'of the two marks relative to the observer, and thelatter is to determine not only. which mark is closer to him, but which devices have the marks arranged at difierent or equal spacing. Thus by interchanging the positions of the marks II and [4 relative to the observer, and by also utilizing spacer sheets of different or equal thickness, a wide variety of tests may be provided. Obviously, the number and arrangement of such devices may be extended to suit the requirements to be met by the person being tested. Fig. 4 shows a cardboard holder 25 in which four different test devices are arranged. For example, a left-hand device 30, Fig. 4, may have the two marks in the same plane, while the next one to the right 3| may have the mark H ahead of the mark 14, while the third from the left 32 may have the mark l4 ahead of the mark H. In all three of these arrangements, however, the spacer sheet [3 is of the same thickness. These three devices thus illustrate the various arrangements of the marks and M. The right-hand device 33 of Fig. 4 on the other hand, has a spacer sheet I 3 which is of a different thickness than the other'devices shown in Fig. 4, thus giving a different depth position of the two marks. Various other sheets of different thicknesses may have the marks arranged as shown in the other three devices illustrated in Fig. 4 to give various arrangements of spacer sheet thickness and depth position of the marks. By such an arrangement, the variation of sheet thickness an the positioning of the marks II and I4 may be carried out to any desired extent.

It is thus apparent from the above description that the present invention provides a simple, effective, and inexpensive device by which the stereoscopic acuity of the person being tested may be quickly, accurately and definitely ascertained. Furthermore, such devices permit a wide variety of such tests to be made to suit the requirements to be met or the individual being tested.

While certain embodiments of the invention have been disclosed, it is to be understood that the inventive idea may be carried out in a number of ways. This application is, therefore, not to be limited to the precise details described, but is intended to cover all variations and modifications thereof falling within the scope of the appended claims.

' I claim:

1. A device for testing stereoscopic acuity comprising, a pair of distinguishable indicia, transparent sheet means for carrying said indicia and through which at least one of said indicia is viewable, said means being of a thickness to space said indicia in depth a distance whose magnitude corresponds to a stereoscopic angle of the same order as the limit of stereoscopic vision of an observer, and a reflection reducing layer carried by said means for covering the indicia nearer the observer to prevent depth relation clues due to reflection at said nearer indicia.

2. A device for testing stereoscopic acuity comprising, a sheet of transparent material, a pair of distinguishable indicia carried by the opposite sides of said sheet and simultaneously viewable by'both eyes of an observer, said sheet being of a thickness to space said indicia in depth a distance whose magnitude corresponds to a stereoscopic angle of the same order as the limit of stereoscopic vision of the observer, and a reflection reducing layer on said sheet for covering the indicia nearer the observer to prevent depth relation clues due to reflection at said nearer indicia.

3. A device for testing stereoscopic acuity comprisingfa sheet of transparent material, a pair of distinguishable indicia carried by the opposite sides of said sheet and simultaneously viewable by both eyes of an observer, said sheet being of a thickness to space said indicia in depth a distance whose magnitude corresponds to a stereoscopic angle of the same order as the limit of stereoscopic vision of the observer, a reflection reducing layer on said sheet for covering the indicia nearer the observer to prevent depth relation clues due to reflection at said nearer indicia, and a. translucent backing for said sheet for covering the other indicia.

4. A device for testing stereoscopic acuity com- 

